In the field of manufacturing a liquid crystal display panel, an alignment solution generally needs to be coated uniformly on a CF (Color Filter) substrate or a TFT (Thin Film Transistor) substrate in accordance with a certain pattern to form an alignment film, so as to make the liquid crystal molecules align orderly under the effect of the alignment film. In the coating process for the alignment solution, with the development of equipments and the manufacturing technology, a method of plating the alignment solution is replaced by a method of spraying the alignment solution, in order to simplify the equipments and the manufacturing process and improve the productive capacity of the equipments and yield of the product. In the spraying process of the alignment solution, a whole line of inkjet heads are used to directly spray the alignment solution to the substrate; after the drops of the alignment solution naturally spread uniformly, the alignment solution is heated to volatilize the solvent in the alignment solution, and then an alignment film with a permanent thickness is formed.
Because the thickness (nano-sized) and uniformity of the alignment film needs to be controlled strictly, a single drop of the alignment solution is controlled to be tiny (nano-sized) during the spraying process of the alignment solution. Specifically, the method for making the drop tiny is as follows: firstly, compressing the alignment solution into the inkjet head under the pressure; secondly, applying a current to a piezoelectric ceramic (namely a vibrator) in the inkjet head to deform the piezoelectric ceramic to disgorge the alignment solution via a nozzle hole; finally, moving the inkjet head to produce drops of alignment solution with high density, so that the drops can spread under the surface tension to form a film.
At present, in the spraying process of the alignment solution, the nozzle hole of the inkjet head should be designed to be tiny-sized, since the single drip must be tiny. However, the traditional alignment solution usually comprises an organic solvent and an alignment polymer dissolved in the organic solvent, and the organic solvent is always volatile, the nozzle hole of the inkjet head will be easily blocked by the alignment polymer since the solvent is volatilized in the spraying process of the alignment solution. As a result, the equipment will be abnormal frequently and the quality of the product will be substantially reduced (normally the amount of the mura increases).
During the spraying process of the alignment solution, when the nozzle hole of the inkjet head is blocked, a user should scrub the inkjet head or put the nozzle hole of the inkjet head into the solvent to dissolve the alignment polymer. However, if the user scrubs the inkjet head, the cleanliness in the equipment will be destroyed. Besides, too much time will be consumed in these two cleaning methods, which may seriously reduce the productive efficiency and the productive quality. At the same time, if the equipment is cleaned in any of these two manners, the cleaning agent is hard to be retrieved, thus leading to the waste of the cleaning agent.